Slide-rule.



No. 845,463. PATENTED FEB. 26, 1907. H. T. HINGKS.

SLIDE RULEn APPLICATION FILED MAY 31,1905.

8 SHEETS-SHEET 1.

N0. 845,463. PATENTBD FEB 26, 1907.

H. T. HINGKS.

SLIDE RULE v APPLICATION FILED MAY31, 1906.

3 SHEETS-SHEET 2.

PATENTED FEB. 26, 1907. H. T. HINGKS.

SLIDE RULE.

APPLICATION FILED MAY 31,1905.

3 SHEETS-SHEET 3.

IIIII I I l WM/o 5 73 mmof conductor.

UNITED STATES PATENT OFFICE.

SLIDE-RULE.

Specification of Letters Patent.

Patented Feb. 26, 1907.

. Applicationfiledhiay 31,1905. SerialNo. 263,175.

To all whom it may concern;

Be it known that I, IIAROLD THORN- THWAITE HINcKs, a subject of the King of Great Britain, residing at Chester, in the county of Chester, in the Kingdom of Eng land, electrical engineer, have invented certain new and useful Improvements in Slide- Scales, for which application has been made in Great Britain, No. 19,061, dated September 3, 1904.

This invention has been specially designed by for me for calculatin electric conductors, in which given three 0 the followin the amperage,the volts lost in circuit, the ength of wire, and the area of wirethe remainlng element can be calculated.

The slide-rule is necessarily based on Ohms law, C=E/R, where C is equal to the current in conductor in amperes, E to the actual fall of pressure or voltage, commonly called drop, and R to the ohmic resistance of the conductor. If C equals E R, it necessarily follows that E equals (JR, or, in other words, the dro of voltage is equal to the current multiplied by resistance. If both sides of the above equation are multiplied by C, we have the equation EC equals 0 R; but EC are volt amperes or watts. Therefore the total loss of power in a circuit, in watts, is equal to the UK losses, and as these can be made fixed quantities it follows that the losses in a cable are entirely independent of the voltage. Following this reasonin for the same power in a conductor it the voltage be doubled only half the amperes will be required, which brings down the C R losses to one-quarter the original amount, which means that the conductor for the same original percentage loss can either be reduced to one-quarter the original size or will carry four times the power. The next point to consider is the resistance of a conductor. There are three points to watch in calculating the resistance: first, the conductivity of metal; second, area of cross-section of conductor; third, length.

The continuous-current constants should be equal to the area in oneone-thousandths of a conductor that will carry an electric currrent one thousand yards with a resistance of one ohm, extra allowance being made for variation of resistance, bad joints, sag, &c., to about 5.7 per cent.

The alternating-current constants for vari ous power factors can be readily found by the following simple equations:

For single phase:

. Continuous current constant Alternating-current constant For two phase, (four-wirez) Alternatingwurrent constant This invention entails the use offive scales, one for each of these four elements, and a fifth a fixed datum-scale for constants dependent on the kind of electric current and the quality of the conductor.

Referring now to the accompanying drawings, Figure 1 is an enlarged view of the area and ampere scale; Fig. 2, an enlarged view of the length-of-circuit scale; Fig. 3, an enlarged view of the constant f and drop-ofvoltage scales; Fig. 4, an enlarged view of the device when fixed in position; Fig. 5, a view of the device in watch form; Fig. 6, a sectional side view of Fig. 5.

Figs. 1-3 show the present invention with the scales separate, and Fig. 4 shows them all together in their working position for clearness. N0 frame or mounting is shown beyond a base-plate a in these figures, and attached concentric to the circular base-plate a is a logarithn'ic scale I) of the volts lost in circuit. Surrounding this and SOLTG distance from it is the datu "ii-scale 0, also fixed to the back, which works in conjunction with the adjusting-point d, n arked on the outer sliding scale 6 Total length of circuit in yards. The datum-scale (i n ight instead he on the outside, so as to turn with the yard-sc ale in conjunction with an adjusting point fixed to the volt-scale b. Surrounding the datuni-scale c is the logarithn ic scale 6 of the total length of circuit in yards (or feet or nieters.) This is niovable in any convenient nanner, and over the blank between the volt-scale and the yard-scale and covering the datum-scale (except at one point where a slot or cut-away part f is cut to see the datum-scale) are two logarithmic scales and hnair.ely, Total amperes in circuit and Area of conductor in one oncthousandths of square inch (or circular 11Li]s,)

phase. now turned round until the three known eleworking in Conjunction with the yard-scale e.

The mode of working is as follows: The constant-scale c is first fixed once for all in its proper position in conjunction with the ad ustingpoint d relatively to the special quality of conductor and circuit, whether continuous or alternating or single phase or poly- The two center scales 9 and h are ments coincide on the four principal scales. The required elemcntthe fourthis now found at once on its respective scale. The circular slide-rule has been so arranged that once the constant is fixed to meet the calculation to be made, whether for simple continuous current or the more complicated alternating current with its phase and power factor, the calculation is the same as far as the operator of the slide-rule is concerned. For instance, suppose twenty K. W. has to be delivered at a factory-for driving it five hundred yards away from the generating-station, loss of power not to exceed five per cent, voltage at generating-station 440. Then if this is a simple parallel continuous-current system the drop in voltage would be 22. The cur- 48.0 amperes nearly. Now three factors are knownnamely, volts lost in circuit 22,total amperes in circuit 48, total length of circuit in yards 500 X 2 equals 1,000. The constant for continuous-current in copper wire is 25.9, which number we turn to the adjustingpoint d, and having fixed 48 on the ampere-scale g opposite 22 on the voltage drop-scale b by revolving it it is easy to see that the area of conductor oppos1te 1,000 yards is fifty-seven one-thousandths of a square inch nearly, or, writing it as a decimal, it equals .057 of a square inch. Suppose in the above calculation it was an alternating current instead of continuous, the voltage being the same, the calculation is made out in exactly the same form, but with a different constant, as above explained. The load being a motor one only, the power factor of the line, it would be fair to assume for the sake of calculation, would be about .80. The constant for copper wire with single-phase alternating current having an .80 power factor is 82.4. Having fixed this, it is found that the area of conductor required is .070 of a square rent to be delivered wo uld be equals inch. Looking it up on the table of the sizes of conductors it will be found that one No. 1 S. W. G. solid wire or 19/15 S. W. G. cable meets the case. Again, suppose in the above calculation it was a three-phase alternating current and the voltage the same. Assum ing the same power factor, the constant would be 18.6. Area of conductor required would be .039 of a square inch.'

lFigs. 5 and 6 show the present invention in watch form. In'these drawings, y' is the glass to which the area-scale h and amperescale" g are secured, which glass is rotatable in the casing k. Z is a fixed ring carrying the length of circuit-scale 6, while m is the back of the device, rotatable on the casing lc and carrying the datum-scale c and voltagescale I).

In thus describing my invention I do not bind myself to this exact arrangement, as it is perfectly obvious that the scales can be turned round by gearing or any other suitable device and, further, that in place of them being in a circle they can be arranged longitudinally side byside, in which case the two'scales previously described as attached to the glass can-pull out together, while the 'scale for the total length of circuit can slide on the basis of the type a equals b/c .or a/b equals c/d or even such formula as a equals 6/0 In each of the above instances the scales are made out logarithmically, but in more complicated formula not necessarily so.

In applying my invention to hydraulics the scales would be, first, datum; second, head; third, area or diameter of pipe; fourth, length of pipe, and, fifth, volume of Water. The factors of other formulae will be easily reco nized in general terms. The scales won (1 be first, datum; second,- ressure, whether of water, electricity, or ot er matter or condition of matter; third, area of transmission means whether i es, wire, or other media; fourth, length of t e transmission means, and, fifth, the quantity, whether of water, electricity, or other matter.

I declare that what I claim is- 1. In a slide-rule of the character described two fixed concentric logarithmic scales; a concentric sliding piece rot'atative about said scales and comprising a logarithmic scale working with the outer of said fixed scale, a second concentric sliding piece with a cut-away part and comprising two further scales rotatative over said fixed scales and working with the inner of said fixed scales whereby a portion of the outer of said two fixed scales can be viewed substantially as described.

2. A sliding scale of the character described comprising a frame a glass rotatative in said frame, two concentric logarithmic scales on said glass there being a cut-away portion on the outer of said scales, a fixed plate or ring a logarithmic scale on said plate or ring said scale working the outer of said concentric scales, and a back piece rotatative in said frame two concentric logarithmic scales on Said back piece, the inner scale working with the inner of the first concentric scales and'the outer showing under the cut-away portion of the outer of said first concentric scales and workin with the scale on the fixed plate or ring su stantially as and for the purpose described.

3. A slide-rule of the character described comprising a base-plate a, a logarithmic scale I), attached to said base-plate and concentric therewith for indicating the olts lost in an electric circuit, a datum-scale c, surrounding the first-named scale at some distance therefrom, fixed to said base, for working in conjunction with a point (1, an outer slidlng logarithmic scale 6, provided with the point (1,

for indicating the total length of said circuit, said scale e surrounding said datum-scale a, two logarithmic scales 9, and h, for indicating the total amperes in said circuit and the area for said circuit res ectively and movable over the blank space hetween said scale I), and said scale a, and covering the datum-scale, except at one portion where a slot f is formed for seeing the datum-scale, said scale g, working in conjunction with said scale I), and said scale h working in conjunction with said scale e.

In witness whereof I have hereunto signed my name, this 18th day of April, 1905, in the presence oftwo subscribing witnesses.

HAROLD T. HINCKS.

Witnesses:

ALGERNON J. YORKE, ARTHUR G. N. KNIGHT. 

